Method of operating portable marine structure



Sept. 29, 1959 METHOD OF OPERATING PORTABLE Filed May 16, 1955 L. B. DELONG ETAL MARINE STRUCTURE 3 Sheets-Sheet 1 INVENTORS 9 0m 3 DE LO/VGEORGE E. SUDEROW Sept. 29, 1959 3 DE LQNG ETAL 2,906,100

METHOD OF OPERATING PORTABLE MARINE STRUCTURE Filed May 16, 1955 3Sheets-Shet 2 F169. F1628. F1010.

INVENTORS LEO/VB. DELO/VG GEORGE E'. SUDEROW MJMQW ATTORNEYS 66 JI c4.14 66 CI P 1959 B. DE LONG ET-AL 2,906,100

METHOD OF OPERATING PORTABLE MARINE STRUCTURE Filed May 16 1955 3Sheets-Sheet 3 FY6116. FIG. 16. FIGJ 4.

I 3 J C2 JILI C1 C4 J4 L4 LI C INVENTORS LEO/VB. DE'LO/VG GEORGE ESUDEROW ATTORNEYS United States Patent Q METHOD OF OPERATING PORTABLEMARINE STRUCTURE Leon B. De Long, Seattle, Wash., and George E. Suderow,Staten Island, N.Y., assignors to De Long Corporation, New York, N.Y., acorporation of Delaware Application May 16, 1955, Serial No. 508,762

13 Claims. (Cl. 61-465) This invention relates to portable, above-watermarine platforms, which may be in the nature of a dock or in the natureof an offshore installation. More particularly, this invention relatesto methods of operating and manipulating apparatus which can be erectedat any selected site as an above-water marine platform, and at anysubsequent time moved to another location for erection thereat, suchapparatus generally embodying the teachings of the co-pendingapplication of Robert W. Pointer, Serial No. 283,567, filed April 22,1952.

In the aforementioned application, there is disclosed a barge having abuoyant hull equipped with a plurality of extensible upright supportingelements or legs. Such legs are there disclosed as caissons which areloosely mounted for vertical movement relative to the hull incorresponding guiding means in the form of wells in the latter. Jacksare mounted on the hull and are releasably engageable with each caissonfor forcefully effecting relative vertical movement in either directionbetween each caisson and the hull, that is, such jacks can extend orretract the caissons. The jacks also can be operated to prevent suchrelative vertical movement. In use of this apparatus, the barge can befloated to any selected marine location and the caissons moved down toengage with the marine bottom while the hull is still afloat.Thereafter, by operation of the jacks, the hull can be raised to anydesired elevation on the caissons and supported thereon, to thus providea stable marine platform which can be used as a dock, as a base fordrilling operations, or for any other appropriate purpose. When it isdesired to move the platform to another location, the hull is lowered bythe jacks back down into the water until the hull is again afloat.Thereupon, the caissons are pulled up by their jacks out of engagementwith the marine bottom and the entire apparatus floated to anothererection site.

Certain problems are encountered in the operation of the aforementionedtype of portable, above-water marine platform. In particular, suchapparatus is presently in use for oil drilling in the Gulf of Mexico,and the marine bottom in certain areas of the Gulf of Mexico, as well asin other locations, is composed for the most part of a deep layer ofalluvial mud, that is, a mixture of silt and water overlying harderunderstrata. In its upper portions, the mud layer may contain as much as80 percent water. while its deeper parts have small water content.Because of the nature of this type of marine bottom, the supporting legsof the aforementioned type of above-water marine platform tend to sinkdeeply into the mud when supporting the weight of the platform and thesupplies and equipment carried thereby. In fact, when the platform isbeing erected, each supporting leg is deliberately driven to refusalinto the marine bottom in order to prevent settling of any one of thesupporting legs deeper into the mud after a prolonged bearing therein.Methods for so driving the supporting legs are described withparticularity in the co-pending application of Showalter et al, SerialNo. 461,454, filed October 2 11, 1954. In actual practice, supportinglegs in the form of tubular steel caissons of the order of 6 feet indiameter have been driven to depths of the order of 70 feet into themarine bottom of the Gulf of Mexico by the methods described in theaforementioned Showalter et al application.

Because the supporting legs of above-water marine platforms of theaforedescribed type are driven deeply into a soft marine bottom, thereare problems involved in pulling the legs out of the mud before theplatform can be moved to another location. When a supporting legpenetrates deeply into a soft marine bottom, the lower portions of theleg tend to become substantially rigid in the mud, so that the lattertends to pack and settle around the legs and substantially freeze theleg in the bottom. Hence, in many cases the mud exerts a gripping actionon the legs that can be overcome only by a pulling force in excess ofthe maximum force that can be exerted by a single jack on a stuck leg.This situation can also exist even when a supporting leg is equippedwith a spread footing. When apparatus of the aforedescribed type iserected in locations where the marine bottom is not particularly soft, aforce in excess of that exertable by a single jack may still be requiredto pull a leg out of the marine bottom. A leg may become so stuck in arelatively hard bottom because the leg has been driven thereinto with apile-driving hammer, or the like. Furthermore, even in an ordinary mudbottom, wherein a leg does not penetrate very deep, the force requiredto pull a leg therefrom may become excessive.

Additional problems exist in the pulling of a stuck leg other than thoseencountered by the inherent limitation of the pulling force of any onejack. In particular, the imposition of a pulling force on a leg createsan equal and opposite reaction force on the barge or platform. In manyinstances, such reaction force is suificient to cause the platform totilt. When such a tilting action occurs, the resulting angularity,though small, between the stuck leg and its guide means on the platformtends to cause a binding action between the guide means and the leg.Such a binding action renders the pulling of a stuck leg even moredifficult. Furthermore, the continued application of a pulling force ona stuck leg, when the latter is at the limit of its possible angularitywith respect to its guiding means on the platform, imposes a strongbending force on the leg. Such a bending force in many instances maybecome large enough to actually bend and damage the supporting leg,whether it is in the form of a caisson as described heretofore or in theform of an openwork tower. It also is pointed out that the large forcesometimes needed to pull a stuck leg also can impose dangerously highstresses in the barge hull. Such stresses can be particularly severewhen the stuck caisson is located adjacent a corner of a generallyrectangular hull, so that the danger of breaking off the corner actuallycan arise.

Consequently, an object of this invention is to provide novel methodsfor pulling stuck supporting legs of a portable, above-water marineplatform of the type under consideration.

It is another object of this invention to provide novel methods forpulling such stuck legs which will avoid a binding action between thelegs and their guiding means on a platform.

It is still another object of this invention to provide methods forpulling a stuck leg of a portable marine platform of the type underconsideration which will prevent the imposition of excessive bendingforces on the stuck leg.

It is another object of this invention to provide methods for pulling astuck leg of a portable marine platform of the type under considerationwhich will prevent the imposition of excessive stresses on the platform.

It is a further object of this invention to provide novel methods forpulling stuck legs of a marine platform of the type described which willenable the imposition of a pulling force in excess of the maximum forceexertable by the corresponding pulling instrumentality.

Other objects and advantages of the invention will become apparent fromthe following description and accompanying drawings, in which:

Figure 1 is an enlarged, fragmentary, vertical sectional viewillustrating jack mechanism of the type which can be utilized forpracticing methods involving this invention. The jack is shown mountedon a marine platform and exerting an upward force on a platformsupporting leg.

Figure 2 is a view corresponding to Figure 1 but showing the jackmechanism exerting a downward force on a platform-supporting leg.

Figure 3 is an elevational view of an erected, generally triangular,marine platform having three supporting legs, the platform being of thetype to which the methods embodying this invention are applicable.

Figure 4 is a plan view of the platform shown in Figure 3, with partsbroken away to illustrate details.

Figure 5 is a perspective view of the platform shown in Figure 3illustrating the normal result of an attempt to pull one of theplatform-supporting legs free of the grip of the marine bottom.

Figure 6 is a vertical sectional view taken substantially on line 6-6 ofFigure 4 and illustrating a step in one of the methods embodying thisinvention.

Figure 7 is a view corresponding to Figure 6 but illustrating a step inanother of the methods embodying this invention.

Figure 8 is a view corresponding to Figure 3 but illustrating arectangular platform having four supporting legs.

Figure 9 is a plan view of the platform shown in Figure 8, with partsbroken away to illustrate details.

Figure 10 is a view corresponding to Figure 8 but illustrating a step ina method embodying this invention.

Figure 11 is a perspective view of the platform illustrated in Figure 8showing the normal result of an attempt to pull one of the supportinglegs free of the grip of the marine bottom.

Figure 12 is a vertical sectional view taken substantially on line 12-12of Figure 9 and illustrating a step of one of the methods embodying thisinvention.

Figure 13 is a view corresponding to Figure 8 but showing the platformlowered back down into the water and afloat before the supporting legsare pulled up from their engagement in the marine bottom.

Figure 14 is a view corresponding to Figure 13 but illustrating thenormal effect of an attempt to pull up one of the supporting legs freeof the grip of the marine bottom.

Figure 15 is a plan view of the platform shown in Figure 13 with partsbroken away. to illustrate details and showing a step in one of themethods embodying this invention.

Figure 16 is an elevational view of the platform shown in Figure 15. a 1

Figure 17 is a plan view of the platform shown in Flgure 13 with partsbroken away to illustrate details, and showing a step in one of themethods embodying this invention.

Figure 18 is an elevational view of the platform shown in Figure 17.

Figure 19 is a view corresponding to Figure 17 and llustrating a step inone of the methods embodying this invention.

Figure 20 is a side elevational view of an erected platform having morethan four supporting legs, the platform being of the type to which themethods embodying this invention are applicable. 7 i '7 i Figure 21 isan end view of the platform shown in Figure 20.

Figure 22 is a plan view of the platform shown in Figure 20, with partsbroken away to illustrate details.

Referring now to Figures 1 and 2 of the drawings, there is shown a jackJ of the type disclosed in the aforementioned Pointer applicationmounted on a platform 49, which ,may be in the nature of a barge havinga buoyant hull, for releasable engagement with a platform supportingelement or leg L. The leg L in this instance is illustrated as a hollowcircular steel caisson that is somewhat loosely slidably guided forsubstantially vertical linear movement relative to the platform 40 in aguiding well 42 that extends vertically therethrough. The guiding well42 is of a diameter slightly greater than that of the caisson mountedtherein so as to somewhat loosely receive and linearly guide the latter.In an actual operating embodiment, the caisson is of the order of sixfeet in diameter uniformly throughout that section of the length thereofreceivable in its well, while the latter is about six feet, one inch indiameter. Consequently, it will be seen that it is possible for the legL to cant slightly in its well 42. In Figures 1 and 2 of the drawings,the clearance between the caisson L and its well 42 has been greatlyexaggerated for illustrative purposes only.

Although all of the supporting legs shown herein have been illustratedas caissons, it is to be understood that this invention is applicable toand may be practiced with hulls or platforms having upstanding,supporting legs of any type, whether of an openwork tower-likeconstruction or of the caisson-like construction shown herein.Furthermore, it will be realized that the invention can be practicedwith supporting elements or legs of any suitable configuration in crosssection.

The jack J is secured to the platform at the well and is disposed insurrounding relation to the leg L. Since a detailed description of suchjack J is given in the afore mentioned Pointer application, a detaileddescription here would be unnecessarily repetitious. It is sufiicient topoint out that the jack shown in Figures 1 and 2 includes verticallyspaced upper and lower gripper sections 44 and 46, each comprising acaisson-surrounding rigid collar or sleeve 48 having a plurality ofinner circumferential channels within which are disposed hollowfluidpressure-constrictable resilient rings 50 for positively yetreleasably gripping the caisson L. Between the upper and lower sections44 and 46 is a caisson-surrounding fluid-pressure-expansiblebellows-like section 52 capable of exerting a powerful but controllableforce to move the upper and lower jack sections apart, while severalpressure-cylinder retractors (not shown) are spaced about and connectedto both the upper and lower jack sections to draw them toward each otherwhen the bellows 52 is exhausted.

Abutment means are provided on the platform 40 to limit both downwardmovement of the lower jack section 46 relative to the platform andupward movement of the upper jack section 44 relative to the platform.In the embodiment of the jack shown herein, the lower gripper section 46is engageable against the deck of the barge 40, while the upper grippersection 44 is fastened to the barge by a plurality of tie rods 54,usually about four such rods being arranged circumferentially about thejack J. The upper gripper section 44 is slidable on the rods 54, butupward movement of such section relative to the rods is limited by heads56 on the latter engageable by the upper gripper section. The connectionbetween the upper gripper section 44 and the rods 54, or the connectionof the rods to the platform 40, is such that the entire jack I can moveslightly in any transverse direction relative to the guiding well 42 andalso can cant with the leg L as the latter cants in its well.

As described more in detail in the aforementioned Pointer application,even jack 1 can be operated to impart Stcp-by-step vertical linearrelative movement in either direction between the leg L and the platform4i).v Thus, for example, in order to move the leg L upwardly relative tothe platform 49, as shown by the upwardly pointing arrow in Figure l,the lower jack section 46 engages the deck of the platform, the upperjack section 44 is engaged with or grips the leg L, and the bellows 52is inflated. It further will be realized that if the leg L is stuck in amarine bottom and the jack J is operated, as shown in Figure 1, in anattempt to pull the leg, there will be a reaction force on the platform40, equal to the force being exerted by the jack on the leg L in anattempt to pull the latter. Such reaction force is indicated by thedownwardly pointing arrow in Figure 1.

When the jack I is being operated to exert a downward force on the leg Lto move the latter downwardly relative to the platform 40, as indicatedby the downwardly-pointing arrow in Figure 2, it will be seen that theupper jack section 44 is engaged against the heads 56 of the tie rods 54while the lower jack section 46 is engaged with or grips the leg, sothat by inflating the bellows 52 the leg will be formed downwardlyrelative to the platform. Again, there is an opposite reaction force onthe platform 40 as indicated by the upwardly-pointing arrow in Figure 2.This operation normally will be carried out only when the leg L isengaged with a marine bottom, and by operating the jack I in the mannershown in Figure 2, the leg'will continue to be driven deeper into themarine bottom until the resistance to further penetration of the legthereinto becomes substantially equal to the force exertable on the legby the jack without lifting the platform. When a plurality of legs areengaged with a marine bottom and have been so driven to refusal,continued operation of the jacks in the manner shown in Figure 2 willserve to raise the platform on the legs.

It also will be seen that the jack I can be operated to prevent anyrelative vertical movement between the leg L and the platform 40. Inthis operation the upper section 44 is engaged with the tie rod heads 56and the leg L and the lower section 46 is engaged with the deck of theplatform 40 and the leg. Normally, the bellows 52 will be fully inflatedto so position the jack sections 44 and 46. As is 'also described indetail in the aforementioned Pointer application, controls (not shown)are provided for a plurality of jacks'to enable their selectiveindividual operation or their operation in unison.

It also is pointed out that other types of jacks which operate onsomewhat the same general principles as the Pointer jack can be employedfor practicing this invention. .Additiona-lly, the methods of thisinvention can be practiced with other types of mechanisms for forcefullymoving upright supporting legs vertically in either di rection relativeto the platform or for restraining such movement, so that the practiceof this invention is not necessarily limited to the employment of a jacktype of apparatus for forcefully effecting relative vertical movementbetween a supporting leg and a platform. It is pointed out, however,that the amount of movementeffecting force developed by any movinginstrumentality is inherently limited by the size of the movinginstrumentality and that economy dictates a limitation on the size ofany moving instrumentality.

Platform having three supporting legs Referring now to Figures 3 and 4of the drawings, there is shown a portable marine platform of the typewith which this invention is concerned. In this instance, the apparatusis shown as a generally triangular buoyant platform 58 having threesupporting legs L1,

L2, and L3, in the form of caissons, extending through correspondingguiding wells in the platform and operated by corresponding jacks J1,J2, and J3 of the aforedescribed type. The supporting legs L are locatedat the corner portions C1, C2, and C3 of the platform 58 in order toprovide stable support for the latter when it is in its erected positionshown in Figure 3 wherein the supporting legs L have engaged andpenetrated at various depths into a marine bottom 60 and the platformhas been elevated above the surface 62 of the water by operation of thejacks I. As stated heretofore, certain marine bottom conditions, such asthose existing in the Gulf of Mexico, require the legs L to penetratequite deeply into a marine bottom before they reach a bearing sufficientto support the weight of the platform when the latter has been elevatedout of the water sufficiently to eliminate or substantially eliminateits buoyancy support, and such deep penetration is shown in Figure 3.

When it is desired to move the erected platform 58 to another location,the problem arises of pulling the supporting legs L loose from themarine bottom 60. i As previously described, no upward pull can beexerted by a jack J on its corresponding supporting leg L withoutexerting an equal and opposite downward reaction force on the platform58. In the present instance, when the platform 58 is elevated out of thewater, as shown in Figure 3, and an upward pull is exerted on any oneleg L by its jack J, the resulting downward reaction force on theplatform will be substantially unopposed, because the platform issupported at only two other locations, i.e., by the other two legs. Theresult will be to tilt the platform 58. Hence, if a platform is ofgenerally triangular configuration and has only three supporting legs,i.e., one at each corner, the platform must be lowered back down intothe water for buoyancy support before the supporting legs can be pulledup.

When the platform 58 has been so lowered by the jacks J and is afloat,the normal mannerof pulling up all of the legs L from the marine bottomis to operate all of the jacks in unison. Before this is done, however,it is desirable to assure that each leg L can be pulled loose from themarine bottom 60 without the use of an excessive pulling force. Hence,the first step is tooperate each jack J in succession in a direction topull its corresponding leg L slightly. If each leg L can be movedupslightly by its jack J, without the corresponding reaction force causingthe platform 58 to tilt excessively, the next operation preferably willbe to operate all of the jacks individually until the lower ends of thedeeper penetrating legs, i.e., L1 and L2 as shown in Figure 3, are onsubstantially the same level as the lower end of the shallowestpenetrating leg, i.e., L3. All of the jacks usually are then operated inunison to pull up all of the legs L at the same rate so that the lowerends of the latter will clear the marine bottom 60 at substantially thesame time. Hence, the platform 58 can float free without being pinned tothe bottom 60 by any one leg L. Thereafter, the entire apparatus can befloated, as by a tug (not'shown) to another erection site.

In many instances, however, it will be found that a leg, e.g. L1, willbe gripped sotightly in the marine bottom 60 that the reaction forcedeveloped by independent operation of its jack J1 in an effort to pullit loose will merely force the corresponding corner portion C1 of theplatform 58 lower into the water, as is shown in Figure 5. This forcefultilting of the platform 58, if continued, not only eventually will causeall the legs L to become tightly bound in their wells or otherequivalent guides, but also obviously will exert a strong bending forceon all the legs. Hence, as previously pointed out, continued efforts topull a stuck leg by its jack might possibly severely dam age all thelegs as well as impose dangerous stresses on all the guiding wells andthose portions of the platform adjacent thereto.

The aforedescribed difliculties can be avoided, however, by the methodsembodying this invention. One of such methods involves counterbalancingthe platform 58 so that it will remain on an even keel, i.e.,substantially level in the water, while a strong upward pull is beingexerted upon the stuck leg L1 by its jack J 1. This leveling of theplatform 58 can be accomplished by releasing the jacks J2 and J3 on thelegs L2 and L3, and slowly adding weight to that portion of the platformremote from the leg L1, i.e., the portion between the legs L2 and L3, ina manner to cause that portion to sink deeper in the water and maintainthe platform substantially level as the corner C1 tends to be pulleddown while the jack J1 is being operated to pull the stuck caisson L1.This added weight may take the form of heavy equipment, e.g., a crawlercrane, portable air compressors, or the like (not shown), carried insome instances upon such a platform, which can be shifted to the generalarea between the two legs L2 and L3 to counteract the tilting effectcaused by the reaction force of the jack J1 on the platform 58. In theevent that such heavy equipment will not be available or will not beheavy enough, the platform 58 can be prefabricated with a number ofinterior buoyance tanks, such as the three tanks T1, T2, and T3 shown inFigure 4, and by controllably flooding the tanks T2, and T3, suflicientweight can be added slowly to that portion of the platform 58 oppositethe corner C1 to maintain the platform level, as shown in Figure 6,while the jack J1 is being operated with increasing force in an attemptto free the stuck leg L1.

When the stuck leg L1 starts to come loose, all of the jacks J areimmediately actuated to grip their legs L and restrain relative verticalmovement between the latter and the platform 58 to hold the platform ina stationary position. That is, the jacks J are operated to prevent thecorner portion C1 of the platform from bobbing up unduly and thustilting the platform sufficiently to cause possible damage to the legs Land/or their wells. While the platform 58 is held in such a stationaryposition, the water ballast is then unloaded from the tanks T2 and T3 orevenly distributed among all the tanks T and the jacks are then operatedto level the platform if it is out of level. Thereupon, all of the jacksJ are operated in unison to control the rise of the platform 58 to itsnormal draft, as indicated, for example, by the dotted line 64 in Figure6, as the tanks T are pumped dry. After its normal draft 64 has beenreached, the jacks J are operated to pull all the legs L clear of themarine bottom 60 as described hereinbefore in order to float theapparatus to another erection site.

During the course of the foregoing operation of freeing the leg L1 fromthe grip of the marine bottom 60 thereon, it will be seen that thepulling force exerted by the jack J1 is opposed primarily by thebuoyancy of the corner tank T1. As stated heretofore, however, thepulling force exertable by any one jack J on its leg L is inherentlylimited by the size of the jack. Consequently, the maximum pulling forceexertable by the jack J1 on the leg L1 may be insuflicient to loosen thelatter in the marine bottom 60. Additionally, this force normally is notgreat enough to force the corner C1 of the platform 58 down into thewater to any great extent below the normal draft 64 of the platform 58.In this connection, the tilt-down of the corner C1 shown in Figure 5 hasbeen greatly exaggerated for illustrative purposes only. Of course, asthe corner C1 is forced deeper and deeper into the water, more and moreof the latter is displaced so that the buoyancy force opposing thepulling force of the jack J1 correspondingly increases. Hence, at themaximum pulling force exertable by the jack J1 without loosening thestuck leg L1, normally there still will be a considerable amount offreeboard at the corner of the plat form 58.

In such an event, wherein the maximum pulling force of the jack J1 isinsufiicient to free the leg L1 by the aforedescribed procedure, thisinvention also provides a method whereby a pulling force in excms ofthat exerable by the jack J1 may be imposed upon the stuck leg L1 in aneffort to loosen the latter from the marine bottom 60. For this purpose,all of the jacks J are disengaged from their respective legs L and allof the tanks T are slowly flooded substantially equally to sink theplatform 58, while maintaining it level, deeper in the water until asubstantially minimum uniform freeboard is obtained as shown in Figure7. At this point, the jack J1 is engaged with the stuck leg L1 torestrain any relative vertical movement between the latter and theplatform 58, and water is slowly pumped from the tank T1. As the tank T1 is slowly emptied of water, the corner portion C1 of the platformbecomes more and more buoyant, and eventually a buoyancy force will beobtained in excess of the maximum pulling force exertable by the jackJ1. This buoyancy force normally will be sufficient to loosen the leg L1from the marine bottom 60. In this connection, it will be seen thatwater is allowed to remain in the tanks T1 and T2 so that the platform58 will not tilt during the deflooding of the corner tank T1. Suchtilting possibly would occur even if the jacks J2 and J3 were engagedwith their legs L2 and L3 because the latter are assumed to be loose,i.e., not stuck, in the marine bottom 60.

As soon as the leg L1 starts to break loose in the marine bottom 60, thetanks T2 and T3 are started to be de-flooded to prevent tilting of theplatform 58. Additionally, at this time, all of the jacks J areappropriately operated to exert opposed forces between their respectivelegs L and the platform 58 to control the latter while it is rising dueto its increased buoyancy. In other words, as the tanks T2 and T3 arebeing defiooded, all the jacks J must be operated to maintain the barge58 substantially level, until all of the tanks T have been de-floodedand the barge is at its normal draft 64 and in a level position. Werethe platform 58 allowed to tilt appreciably during the foregoingprocedure, possible damage to the legs L or to the structure of theplatform obviously could occur.

It will be seen that in some instances, more than one of the legs Lmight be stuck quite tight in the marine bottom 60. In the event that itis found that all of the legs are so stuck, after the platform 58 hasbeen lowered back down into the water until it is afloat, all of thejacks J can be operated in unison to the maximum extent of their pullingforce in an effort to free the stuck legs. This simultaneous pullingoperation of all of the jacks I obviously will force the entire platform58 deeper into the water while maintaining it substantially level.Consequently, if one of the stuck legs L starts to break loose, all ofthe jacks J must be operated in a manner to maintain the platform 58 onan even keel, while the jacks J are being operated to allow the platformto rise on the legs to its normal draft 64.

If the foregoing procedure does not loosen any or all of the three stucklegs L, the jacks I can be disengaged from the legs and all three tanksT evenly flooded until the platform 58 has sunk to a minimum freeboard,as shown in Figure 7. Thereupon, the jacks J are re-engaged with thelegs L to restrain any relative vertical movement between the latter andthe platform and all the tanks T are evenly and slowly de-flooded. Bythis procedure a buoyancy pulling force can be developed on each of thethree stuck legs normally greatly in excess of the pulling forceexertable by any one of their jacks J. Again, if any one of the threestuck legs L starts to break loose in the marine bottom 60, all thejacks J must immediately be operated in a manner to maintain theplatform 58 level.

Assuming that one of the three stuck legs L has been loosened so that itcan be pulled up readily by the operation of its jack J, there willremain two legs stuck in the mud. Thus, for example, assuming that legL1 has been loosened and that legs L2 and L3 remain stuck,

,the latter two legs can be loosened by procedures similar to thoseoutlined hereinbefore. First of all, an attempt can be made to freeeither or both of the two stuck legs L2 and L3 by exerting simultaneouspulling forces thereon by their respective jacks J2 and J3. To avoidtilting of the platform 58, the jack J1 is released and weight slowlyadded to the corner portion C1 of the platform, as by flooding the tankT1, to cause such portion to sink deeper into the water and thusmaintain the entire platform 58 substantially level as the two cornerportions C2, and C3 are being forced deeper into the water by thereaction force exerted thereon by the jacks J2 and J3 in their effortsto pull the two stuck legs L2 and L3. If either or both of the two legsL2 and L3 are loosened in the marine bottom 60 by this procedure, thetank T1 is immediately started to be de-flooded to prevent tilting ofthe platform. Also, as the corner C1 tends to rise because of itsincreasing buoyancy, all of the jacks J are operated in a manner tocause the platform 58 to rise to its normal draft 64 without becomingappreciably out of level.

If the aforedescribed procedure fails to loosen the two stuck legs L2and L3, all of the jacks I can be released, and all of the tanks Tflooded substantially equally to thus sink the platform 58 deeper in thewater until it has substantially minimum freeboard. At this time, thejacks J2 and J3 are operated to restrain relative vertical movementbetween the platform 58 and the legs L2 and L3 and the two tanks T2 andT3 are slowly tie-flooded. Thus, the buoyancy of the two corner portionsC2 and C3 will slowly increase until an upward pulling force is exertedon the two stuck legs L2 and L3 in excess of the maximum pulling forceexertable thereon by their respective jacks J2 and J3. As previouslystated, such force normally will be suflicient to loosen either or bothof the stuck legs L2 and L3 in the marine bottom 60'. Again, when eitheror both of the two stuck legs L2 and L3 start to break loose in themarine bottom, the tank T1 is started to be de-flooded and all of thejacks are operated to maintain the platform 58 substantially level whileit rises to its normal draft 64.

Platform having four supporting legs Referring now to Figures 8 and 9 ofthe drawings,

' there is shown another type of portable marine platform embodyingapparatus with which this invention is concerned. In this instance, theapparatus is shown as a generally rectangular buoyant platform 66 havingfour supporting legs L1, L2, L3, and L4, one located adjacent eachcorner portion C1, C2, C3, and C4, in the form of caissons extendingthrough corresponding guiding wells in the platform and operated byjacks J1, J2, J3, and J4 of the aforedescribed type.v The platform 66 isshown erected in Figure 8 wherein the supporting legs L have engaged andpenetrated at various depths relatively deeply into a soft marine bottom68, and the platform has been elevated above the surface 70 of the wateron the legs by operation of the jacks J.

As hereinbefore described with reference to a threelegged triangularplatform, when the platform 66 is to be moved to another location, it isdesirable to assure that each leg L can be pulled up easily out of themarine bottom 68 before all the legs are raised in unison as describedhereinbefore. When a platform is supported by more thanthree leg, suchinitial procedure can be accomplished before the platform is loweredback down into the water into its floating condition. This is highlydesirable since it shortens the time of transition of the apparatusafter the platform is in the water from its bottom-pinned to its freefloating condition, which shortened transition time is greatlyadvantageous if heavy seas are running. Hence, before the platform 66 islowered back down into the water by operation of the jacks J, each jackcan be operated in succession in a direction to pull its correspondinglegL slightly because the platform will be substantially stablysupported by the other three legs. In other words, the reaction force ofany one jack J, if not excessive, will not force down the correspondingcorner C of the platform 66 because of the counter balancing weight ofthe diagonally opposite corner portion and the weight and bottom-grip onthe leg thereat 10 when the jack of the latter restrains verticalmovement of the same relative to the platform.

If a leg L can be moved up slightly by its jack J, as indicated, forexample, by the dotted line showing of leg L4 in Figure 10, the legwillbeable to bepulled up completely by its jack when the platform 66 islowered back down into the water. Frequently, however, theaforedescribed testing procedure will reveal that one, orpossibly more,of the legs L is gripped tightly by the marine bottom 68, so that theaforedescribed testing procedure merely serves to force down thecorresponding corner C of the platform 66 when theleg-pulling force ofthe jack J begins to overcome the aforedescribed counterbalancing effectof the diagonally opposite corner portion and leg thereat. In such anevent, the following procedure may first be attempted in order to. tryto free a stuck caisson.

First of all, all of the loosened legs L are driven back down to a firmbearing into the marine bottom 68 by operation of their jacks J. Thus,for example, assuming that leg L1 is stuck and the remaining legs L2,L3, and L4 are loose, after the aforedescribed testing procedure thelatter legs L2, L3, and L4 are driven back to a firm bearing, i.e.,their original bearing, in the marine bottom by their respective jacksJ. Thereupon, the jacks on the legs L2, L3, and L4 are engaged withtheir legs in a manner so that no relative vertical movement can occurbetween the three legs L2, L3, and L4 and the platform 66. The jack J1for the stuck leg L1 then is operated to exert a pulling force on thelatter, with the consequent development of an equal downward reactionforce on the corner portion C1 of the platform 66. This reaction force,which obviously urges the corner portion C1 downwardly, is opposedprimarily by the support afforded by the two legs L2 and L4, so that thereaction force also tends to raise the diagonally-opposite cornerportion C3 of the platform 66. If the leg L3 holds fast in the marinebottom 68, the platform 66 will not tilt, but if the leg L3 pulls loosefrom the marine bottom, and it is assumed to be loose therein, thecorner C1 will drop and the corner C3 will rise, and thus'tilt theplatform as shown in Figure 11. As aforedescribed, such a condition ishighly undesirable, because all the legs L will immediately start tobind in their wells as soon as the limit of angularity between each legand its well is reached. This binding action serves to reduce theeffective pulling force exertable on the leg L1 by its jack J1 and alsoto impose strong and possible damaging bending forces on all the legsand possibly damaging stresses on their wells and associated platformstructure.

In order to eliminatethe aforedescribed tendency of the platform 66 totilt if the leg L3 pulls loose, weight is added slowly to the oppositecorner portion C3 of the platform, as the pulling force of the jack I1is increased, in order to counterbalance such tilting effect. Asdescribed before, such weight can take the form of heavy equipment (notshown) which can be shifted to the corner C3. In the event that theweight of such equipment is not suflicient to counterbalance the tiltingtendency or such equipment is not available or shiftable, it isdesirable for the platform to be provided with interior compartments ortanks T, as shown in Figure 9,

into which water can be pumped for adding weight thereto. Hence, as isshown in Figure 12 of the drawings, sufficient water has been added tothe tank T3 to counteract the tendency of the platform 66 to tilt whenthe jack I1 is being operated in a direction to pull the stuck leg L1.Thereupon, a large pulling force can be exerted effectively by the jackJ1 in an effort to loosen the leg L1 in the marine bottom 68.

It is obvious that the foregoing procedure will exert large stresses inthe platform 66, and if the latter does not possess suflic'ientstructural strength, there actually may be a danger of breaking off thecorner portion C1. Hence, if the platform 66 cannot safely absorb thestresses 11 imposed therein when the jack J1 is operated with itsmaximum pulling force, the latter must be operated with a reduced force.

Even when the jack I1 is operated with its maximum pulling force in aneffort to loosen the stuck leg L1 by the foregoing procedure, in someinstances such procedure will not serve to loosen the stuck leg. In thatevent, the following procedure may next be employed, assuming that theplatform 66 has sufficient structural strength to enable the employmentof such procedure.

The jack J1 is engaged with the leg L1, to prevent relative verticalmovement between the latter and the platform 66, and simultaneously thejacks on the other three legs L2, L3, and L4 are operated in a manner tolift the platform 66 on such legs. By means of this procedure, it willbe seen that the combined forces of all three jacks J2, J3, and J4 canbe utilized in an effort to loosen the stuck leg L1. If the combinedlifting forces of the jacks J2, J3, and J4 fail to loosen the stuck legL1, the jack J1 of the latter is operated to exert a pulling force onthe leg L1 while the other three jacks are being operated to exertlifting forces on the platform 66. Thus, the combined efforts of allfour jacks can be employed to loosen the leg L1. It will be realized,however, that the upward forces so exertable on the leg L1 through theplatform 66 by the jacks J2, J3, and J4 are limited by the weight of theplatform. Of course, both of these procedures exert tremendous stressesin the platform 66 so that due regard must be had to its structuralstrength, Additionally, the platform 66 may also have a tendency to tiltdownwardly at the corner C1 and to rise at the opposite corner C3 duringsuch procedures. Such a tendency also can be restrained by thehereinbefore described counterbalancing steps, eg by pumping sufficientwater into the tank T3 to counterbalance the pulling force on the legL1.

The aforedescribed procedure of utilizing the combined force of all ofthe jacks J to loosen a single leg can also be employed if all, or anylesser number, of the legs are stuck in the marine bottom 68 byoperating on each stuck leg in succession. Although the foregoingprocedure of utilizing the combined force of all of the jacks J toloosen a single stuck leg L is possible, marine platforms of the typeunder consideration normally are not designed to withstand such extremestresses. The imposition of such extreme stresses can be avoided,however, by lowering the platform 66 back down into the water until itis afloat at normal draft 72, as shown in Figure 13, and then utilizingthe following procedures in an effort to free stuck legs.

Assuming that leg L1 is stuck in the marine bottom 68 and that theremaining legs L2, L3, and L4 are loose therein, the exertion of apulling force by the jack J1 on the stuck leg L1, with the remainingjacks J2, J3, and J4 disengaged from their respective legs, serves toforce the corner C1 deeper into the water with a resulting undesirabletiling of the platform 66, as exaggeratedly shown in Figure 14. Thetendency of the platform 66 to so tilt can be avoided, however, by thehereinbefore described procedures of adding suflicient weight to thediagonally opposite corner C3, as by slowly flooding the tank T3 asshown in Figure 15, to maintain the platform level as shown in Figure 16as the pulling force of the jack J1 is increased and forces the cornerC1 deeper in the water. It will be seen that during this procedure, theplatform 66 is supported in the water by the uniform pressure of thelatter thereagainst, and that the downward reaction force of the jack J1is opposed primarily by the buoyancy of the corner portion C1 of theplatform so that no concentrated and damaging stresses are imposed onthe latter by such procedure. During this procedure, the tanks T2 and T4can be flooded selectively and partially, if need be, in order tocounteract any tendency of the platform to tilt down at the oppositecorner C4 or C2, respectively.

If by this procedure, the leg L1 starts to pull loose, the remainingjacks J 2, J3, and J4 are immediately operated to restrain verticalmovement between the legs L2, L3, and L4 while the tank T3 is deflooded,and also the tanks T2 or T4, if also flooded. Thereupon, the jacks J areoperated to level the platform 66, if necessary, and to control the riseof the platform to its normal draft 72.

If all or more than one of the legs L is stick in the marine bottom,attempts can be made to free such legs by operating on them insuccession in accordance with the foregoing procedure. Still anotherprocedure can be utilized, however. When the platform is afloat, thejacks for such stuck legs can be operated in unison to exert pullingforces on the stuck legs while counterbalancing any tilting tendenciesof the platform 66 by adding weight to appropriate portions of theplatform as described hereinbefore with reference to a three-leggedplatform. Thus, for example, if the legs L1 and L2 are stuck, whiletheir jacks J1 and J2 are being operated in unison to pull them, thetanks T3 and T4 are flooded sufficiently to maintain the platform 66level as that side of the platform extending between the corner C1 andC2 sinks deeper in the water.

As aforedescribed, the maximum pulling force exertable by a single jackon its leg in many instances will be insufiicient to loosen a leg thatis stuck in a marine bottom. Accordingly, if the foregoing procedure isunsuccessful, the following procedure may be utilized in an attempt tofree a stuck leg, e.g., L1. All of the jacks J are disengaged from theirlegs L and all of the tanks T are slowly and uniformly flooded as shownin Figure 17 until the platform 66 has sunk into the water to a minimumfreeboard, as shown in Figure 13. At this point the jack J1 is operatedto grip or engage its leg L1 in a manner to prevent relative verticalmovement between the latter and the platform 66. The tank T1 then isslowly de-flooded, as shown in Figure 19, so that the increased buoyancyof the corner portion C1 of the platform 66 will exert an upward pullingforce on the stuck leg L1 in excess of that exertable thereon by thejack J1. In the event that this buoyancy force is insufficient to loosenthe leg L1, the tanks T2 and T4 may be slowly and controllablyde-flooded, in a manner to prevent tilting of the platform 66 towardeither of the corners C2 or C4, to resultingly increase the upwardbuoyant force on the leg L1. If necessary, additional water can bepumped into the tank T3 to prevent upward tilting of the corner C3because of the increasing buoyancy of the tanks T2 and T4.

The foregoing procedure, i.e., first de-flooding tank T3 and thende-flooding tanks T2 and T4, if necessary, usually will be quitesuflicient to loose the stuck leg L1. As soon as the leg L1 starts toloosen in the marine bottom, the tank T3, and T2 and T4 if flooded, iscontrollably de-flooded and all of the jacks J are operated on theirlegs to maintain the platform 66 level while it is rising due to itsincreasing buoyancy.

Similar procedures can be employed to free more than one stuck leg,either by operating on them in succession, or in unison as describedhereinbefore with reference to a three-legged platform. Thus, forexample, if the legs L1 and L2 are stuck, after the platform 66 has beensunk to a minimum freeboard, the jacks J1 and J2 are operated torestrain downward movement of their legs relative to the platform, whilethe tanks T1 and T2 are slowly de-flooded.

Platform having more than four supporting legs Substantially all of theforegoing procedures are likewise applicable to marine platforms of thetype under consideration having more than four supporting legs. Thus,for example, as shown in Figures 20 to 22, a generally rectangularmarine platform 74 may have twelve such supporting legs L1 to L12arranged in two rows extending along both longitudinal sides of theplatform.

. V 13 1 When the platform 74 is in its erected position, as shown inFigures 20 and 21, with the legs L penertating' at various depths intothe marine bottom 76, each leg is first tested by its jack J to see ifit can be loosened in the marine bottom before the platform is loweredback down into the water. Such testing procedures were outlinedhereinbefore with reference to the platform shown in Figure 8. V

In this connection, it will be seen that the maximum pulling force ofeach jack 1 can be exerted on its corresponding leg L with substantiallyno possibility what ever of causing the platform 74 to tilt because ofthe geometrical arrangement of the legs on the platform. Even if themaximum'pulling force of the jack I is exerted on a corner leg, such asleg L1, it will be seen that any tendency of the corresponding corner ofthe platform 74 to be pulled down, because of the resulting reactionforce on the platform, will be completely counteracted by the weight ofthose portions of the platform on the opposite side of a line,connecting the legs L2 and L3, from the leg L1.

In the event, however, that a leg L is stuck so fast in the marinebottom 76 that the maximum pulling force of its jack J is insuflicientto loosen the leg, the following procedure can be used to exert apulling force on the stuck leg in excess of the pulling force exertablethereon by its jack. I

Thus, for example, assuming that the leg L1 canno be freed from themarine bottom 76 by its jack J 1, the latter jack is engaged withits legLlto prevent downward movement of the latter relative to the platform 74and then all of the other jacks J2 to I12 are operated to lift theplatform on the legs L2 to L12, thus utilizing the combined force ofeleven of, the jacks I in an effort to free the stuck'leg L1. Of course,as heretofore mentioned, the combined force of the aforementioned elevenjacks I2 to 112 effective to pull the stuck leg L1 is limited somewhatby the Weight of the platform 74 and the equipment carried thereon andtherein. Nevertheless, the aforementioned combined force normally isgreatly in excess of the pulling force of any single jack 1. If theforegoing procedure is not successful in freeing the stuck leg L1, thejack J1 on the stuck leg can be operated to pull the leg L1 while all ofthe other eleven jacks J2 to 112 are being operated in a manner to liftthe platform.

Of course, the employment of the foregoing procedure is limited by thestructural strength of the platform 74, and in particular if a cornerleg L1, L2, L11, or L12 is stuck, there may be some danger of actuallydamaging the structure of the platform by any of the foregoingprocedures. Accordingly, if any of the foregoing procedures do notsucceed in freeing a stuck leg by exterting pulling forces thereon tothe maximum extent permitted by the structural strength limitations ofthe platform 74, the platform should be lowered back down into the water78 until it is afloat, and the following procedures employed.

Again, assuming that leg L1 is stuck in the marine bottom 76, the jacksJ2 to I12 are released and the jack I1 is operated to exert a pullingforce. on the stuck leg. As the pulling force of the jack I1 isincreased, the resulting reaction force will tend to force the cornerportion C1 of the platform 76 deeper into the water. To counteract thistilting of the platform 74 and to maintain it on an even keel While thejack I1 is being operated in an effort to free the stuck leg Ll, weightis added or shifted to the opposite side of the platform. Thus, forexample, the ballast tanks T2 and T4 may be partially floodedsufliciently to mtintain the platform on an even keel athwartship. Ifnecessary, the tanks T11 and T12 may also be sufliciently partiallyflooded in order to maintain the platform on an even keel fore and aftor longitudinally.

Much the same procedures may be followed in the t 14 event that a legremote from a corner of the platform is stuck. Thus, for example,assuming thatleg L6 is stuck in themarine bottom, while the jack I6 isbeing operated in an effort to free the stuck leg L6 weight must beshifted or added to the other side of the platform in order to maintainthe latter on an even keel athwart ship. Hence, the tank T5 may besufficiently partially flooded to maintain such an even keel. It isobvious that when a stuck leg is located at a position remote from theends of the platform 74, there usually will be no necessity for floodingany of the end tanks to maintain the platform 74 on an even keellongitudinally. When a stuck leg starts to pull loose, all of the jacksare immediately operated to engage their corresponding legs in order tohold the platform 74 stationary while the interior tanks which wereflooded are de-flooded and then all of the jacks are operated tomaintain the platform on an even keel while it rises to its normaldraft.

If any of the foregoing procedures do not succeed in freeing a stuckleg, the following procedure may then be followed. A number ofsymmetrically disposed tanks, such as the tanks T1, T2, T11, and T12 areslowly and evenly flooded untilthe platform sinks levelly into the waterto a minimum freeboard. If necessary, additional tanks, such as tanksT3, T4, T9, and T10 may also have to be flooded in order to obtain sucha minimum freeboard. After such a minimum freeboard is had,

the jack for the stuck leg is then operated to engage 1 therewith. Thus,for example, assuming that leg L1 is stuck in themarine bottom, the jackI1 is engaged therewith, whilethe other jacks are disengaged from theirrespective legs, and the tank T1 then is slowly de-flooded so that theincreasing buoyancy of the corner C1 of the platform exerts aprogressively increasing upward force on thestuck leg- L1. .Additionaltanks, such as T2 and T3, also can be slowly de-flooded in the eventthat the buoyancy force of the tank T1 is insuflicient to free the stuckleg L1 from the grip of the marine bottom 76. In the event that theplatform tends to tilt in any. direction during the foregoing operation,other tanks may be flooded or de-flooded as necessary in order tomaintain the platform level. As before, when the stuck leg L1 starts tobreak loosefrom the marine bottom, all of the jacks are operated to griptheir respective legs L in order to hold the platform stationary whilethe tanks Twhich had been flooded aredeflooded. Thereupon, all of thejacks are operated to control the rise of the platform to its normaldraft.

If more than one leg is found to be stuck in the marine 'bottom, theycan be freed by operating on them in succession in accordance with theforegoing procedure, or in unison in accordance with comparableprocedures hereinbefore with reference to three-legged and fourleggedplatforms.

It will be realized that all of the foregoing methods can be practicedwith non-buoyant platforms that are detachably carried, for example, ona barge and have the supporting legs of the platform disposed outboardof the peripheral outline of such barge for effective operation of suchlegs. Those methods described above wherein the platform is afloat Whilea stuck supporting leg is being pulled, still can be practiced with anon-buoyant barge-carried platform by securely fastening the latter tothe barge. Of course, in all of those methods wherein a stuck leg isbeing pulled while the platform is up in the air, so to speak, theplatform can be non-buoyant and the barge used only for installation andtransportation of the platform. 7 7

It thus will be .seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that variouschanges may be made in the methods described and illustrated herein forthe purpose of illustrating the principles of this invention withoutdeparture from such principles. Accordingly, this 45 invention includesall modifications encompassed within the spirit and scope of thefollowing claims.

We claim:

1. The method of pulling loose from a gripping marine bottom asupporting leg of a portable above-water marine platform which includesa platform-like buoyant body having at least three substantially uprightmarine-bottomengageable supporting legs extensibly mounted on the bodyfor only substantially perpendicular movement relative thereto, andfurther having means for selectively and forcefully extending andretracting the legs or restraining the latter against movement relativeto the body, and starting with the legs engaged with the marine bottom,at least a portion of the weight of the body supported on the legs, andat least one of the legs stuck against pullout in the marine bottom, thesteps comprising: lowering the body on the legs and buoyantly supportingthe body in the water substantially perpendicular to the one stuck leg;exerting opposed forces between the body and the one marine-bottom-stuckleg in a direction to raise the latter relative to the body whilerendering the remaining legs freely extensible or retractable relativeto the body; and counteracting the tilting effect of such forces on thebody and maintaining the latter substantially perpendicular to the stuckleg during the exertion of such forces by adding weight to portions ofthe body remote from the one leg.

2. The method defined in claim 1 in which the weight is added byshifting weight from other portions of the body.

3. The method defined in claim 1 in which the weight is added by addingwater ballast.

4. The method defined in claim 1 in which the body is generallytriangular and has three supporting legs, one located adjacent each apexof the body, and the weight is added at a location generally adjacentthat side of the body opposite the one leg.

5. The method defined in claim 1 in which the body is generallyrectangular and has four supporting legs, one located adjacent eachcorner of the body, and the weight is added at a location generallyadjacent that corner of the body diagonally opposite the one leg.

6. The method defined in claim 1 in which the body is generallyrectangular and has more than four supporting legs arranged generally intwo rows extending along the opposite longitudinal sides of the body,and the weight is added to that side of the body opposite the row inwhich the one leg is located.

7. The method defined in claim 1 in which the body is generallyrectangular, has more than four supporting legs arranged generally intwo rows extending along the opposite longitudinal sides of the body;the one leg is located between one end of the body and the transversecenter line thereof; and the weight is added to that side of the bodyopposite the row in which the one leg is located in order to maintainthe body substantially at right angles to the one leg athwartship andthe weight is also added at a location adjacent the other end of thebody to maintain the latter substantially at right angles to the one legfore and aft.

8. The method of pulling loose from a gripping marine bottom asupporting leg of a portable above-water marine platform which includesa platform-like body having at least three substantially uprightmarine-bottom-engageable supporting legs extensibly mounted on the bodyfor while freely permitting relative movement between the legs and thebody; decreasingly the buoyancy support of the body to lower the latterrelative to the surface of the water into a position substantially,perpendicular to the one stuck leg; fixing the one marine-bottom-stuckleg against extensible movement relative to the body; increasing thebuoyancy support of that portion of the body adjacent the one stuck legto thereby impose an upward force on the latter; and maintaining thebody substantially perpendicular to the one stuck leg during the step ofincreasing the buoyancy support by adjusting the buoyancy support ofother portions of the body.

9. The method of pulling loose from a gripping marine bottom asupporting leg of a portable above-water marine platform which includesa platform-like body having at least four substantially uprightsupporting legs extensibly mounted on the body for only substantiallyperpendicular movement relative thereto at locations outlining at leasta quadrilateral geometric figure, and further having means forselectively and forcefully extending and retracting the legs orrestraining the latter against movement relative to the body, andstarting with the legs engaged with the marine bottom, at least aportion of the weight of the body supported on the legs, and at leastone of the legs stuck against pullout in the marine bottom, the stepscomprising: exerting opposed forces between the body and the onemarine-bottom-stuck leg in a direction to raise the latter relative tothe body while stably supporting the latter on the other legs; andcounteracting the tilting effect of such forces on the body andmaintaining the latter substantially perpendicular to the one stuck legduring the exertion of the opposed forces by adding weight to portionsof the body remote from the one leg.

10. The method defined in claim 9 in which the weight is added byshifting weight from other portions of the body.

11. The method of pulling loose from a gripping marine bottom asupporting leg of a portable above-water marine platform which includesa platform-like body having at least four substantially uprightsupporting legs extensibly mounted on the body at locations outlining atleast a quadrilateral geometric figure, and further having means forselectively and forcefully extending and retracting the legs orrestraining the latter against movement relative to the body, andstarting with the legs engaged with the marine bottom, a least a portionof the weight of the body supported on the legs, and at least one of thelegs stuck against pullout in the marine bottom, the steps comprising:fixing the one marine-bottom-stuck leg against extensible movementrelative to the body; and exerting opposed forces between the body andthe other legs in a direction to raise the body on the latter.

12. The method defined in claim 11 including the additional step,carried out simultaneously with the force exerting step, of exertingopposed forces between the body and the stuck leg in a direction toraise the latter relative to the former.

13. The method defined in claim 11 wherein the legs are mounted for onlysubstantially perpendicular movement relative to the body and includingthe additional step of maintaining the body substantially perpendicularto the one stuck leg during the force exerting step by adding weight toportions of the body remote from the one stuck leg.

References Cited in the file of this patent UNITED STATES PATENTS1,000,152 Correll Aug. 8, 1911 2,775,869 Pointer June 1, 1957 V FOREIGNPATENTS 606,033 Great Britain Aug. 5, 1948 713,298 Great Britain Aug.11, 1954

